1. Field of the Invention
The present invention relates to a grinding wheel in combination with a grinding ring, and more particularly to a grinding ring having multiple teeth formed on a peripheral edge of the grinding ring and a tubular extension centrally formed on a center of the grinding ring such that when the grinding ring is combined with the grinding wheel, extension of the teeth of the grinding ring into the grinding wheel is able to enhance the combining force therebetween.
2. Description of Related Art
A conventional grinding wheel assembly is shown in FIG. 15, which includes a grinding ring 10a and a grind wheel 20a. The grinding ring 10a is a shallow disk and has a central hole 11a, a tubular extension 12a extending from a peripheral edge defining the central hole 11a, a first annular extension 13a extending from an outer periphery of the tubular extension 12a, a flange 15a formed around an outer peripheral edge of the first annular extension 13a and a second annular extension 14a extending from an outer periphery of the flange 15a. The grinding wheel 20a has a hole 21a corresponding to the flange 15a. When the grinding ring 10a is to be combined the grinding wheel 20a, the flange 15a of the grinding ring 10a is extended into the hole 21a and an adhesive is applied to secure the engagement between the flange 15a and an inner periphery defining the hole 21a. 
Another conventional grinding wheel assembly is shown in FIG. 16 of the attached drawings, which includes a grinding ring 30a and a grinding wheel 20a. The grinding ring 30a is a shallow disk and has a central hole 31a, a tubular extension 32a, an annular extension 33a extending from an outer periphery of the tubular extension 32a and teeth 34a formed on a peripheral edge of the annular extension 33a. When combining the grinding ring 30a and the grinding wheel 20a is necessary, the teeth 34a is inserted into the grinding wheel 20a and an adhesive is applied from the central hole 31a to secure the engagement therebetween.
A further conventional grinding wheel assembly is shown in FIG. 17 of the attached drawings, which includes a grinding ring 40a and a grinding wheel 50a. The grinding ring 40a is a shallow disk and has a central hole 41a, a tubular extension 42a extending from a periphery defining the central hole 41a, an annular extension 43a extending from an outer periphery of the tubular extension 42a and teeth 44a extending from a bottom face of the annular extension 43a, each tooth 44a having a barb 441a formed on a free end of the tooth 44a and a peripheral side 45a formed around the teeth 44a. The grinding wheel 50a is composed of multiple grinding plates 51a superposed on top of one another to form a circle. When the combination between the grinding wheel 50a and the grinding ring 40a is necessary, the teeth 44a is inserted into the grinding wheel 50a to allow the grinding ring 40a to cover all the grinding plates. Then an adhesive is applied from sides of the grinding ring 40a to securely engage the grinding plates of the grinding wheel 50a and combine the engagement between the grinding ring 40a and the grinding wheel 50a. 
Although each of the grinding wheel assemblies initially has a firm combination between the grinding ring and the grinding wheel, there are still disadvantages making the combination unreliable, which are:
The grinding ring of FIG. 15 is made of plastic and has an area substantially the same as that of the grinding wheel. The adhesive seems the only solution to securely combine the engagement therebetween. Accordingly, the grinding ring is easily engaged with the polishing object and thus the surface of the polishing object is easily damaged. Further, the engagement between the grinding ring and the grinding wheel by the adhesive is not able to provide effective combining force and the grinding ring is easily fallen from the grinding wheel.
The grinding ring of FIG. 16 is made of metal such that using a mold to produce such a grinding ring with teeth formed on the periphery of the grinding ring. Besides, there is only the extension of the teeth into the grinding wheel to secure the engagement between the grinding ring and the grinding wheel, horizontal extension is not provided to the grinding ring such that when the grinding ring is polished, the grinding ring is easily broken due to lack of strength, which leads to a bad influence to the polishing surface of the object to be polished.
The conventional ring in FIG. 17 is made with a mold, temperature and pressure must be strictly controlled, resulting in high cost. Further, when the grinding ring is used with the grinding wheel having multiple grinding plates superposed together, the grinding ring is easily overturned due to lack of strength.
To overcome the shortcomings, the present invention intends to provide an improved grinding ring in combination with a grinding wheel.